Heavy ship SAS oscillation

[THX1138]

The SAS on my heavy ships overshoots its target and I have to alt+tab out of the game and leave it oscillating for 20+ minutes. It's because the SAS is stupid and doesn't start countering the movement until it's way too late. In fact, it keeps tugging and tugging until it's too late and then it starts tugging the other way. I could do a better job myself but boy is it boring. I'd rather play a truck driving simulation. It's fine if all your ship is small but mine isn't. I shouldn't have to launch unreasonable amounts of RCS propellant or reaction wheels to counter badly programmed SAS that doesn't take into account the power of available reaction wheels.

[Wanderfound]

If you time accelerate (normal on-rails time, not physics warp) for a moment the oscillation will cease.

[THX1138]

That exploit is finnicky. Sometimes coming out of time warm imparts a seemingly random direction to my vessel which is not conducive to the precision I need for docking.

[Bill Phil]

Hint: don't build too big. It probably has to do with part count or an over stressed physics simulation going on.

Btw, if you think THIS is bad, you should've seen pre-0.21 SAS...

[Wanderfound]

If you're docking large craft, point the docking ports towards each other while you're still far off, timewarp freeze the inactive ship and control the smaller, more agile ship during the docking. Disable SAS on the inactive ship.

If both ships are huge monster wobbly space stations, then they'll still be hard to dock, but that's as it should be.

Despite all the above, docking ports could use some beefing up. Wobbly ports is the main cause of space station jiggle; they're much less rigid than they should be, and no easy way to reinforce them.

[kmacku]

Despite all the above, docking ports could use some beefing up. Wobbly ports is the main cause of space station jiggle; they're much less rigid than they should be, and no easy way to reinforce them.

At least this. Right now, this is my biggest "complaint" that doesn't involve bugs/glitches/crashes. Docking ports in general need to be strengthened; I can deal with massive ship wobble (nothing a few struts can't fix). But when your interstellar ship is basically a daisy chain on rockets...I dunno. And my Minmus station is kinda wobbly like a big dumb jellyfish trying to get people to read its pamphlet at this point.

[Wanderfound]

As a stopgap solution for now: when moving large stuff that was assembled in orbit, don't push, pull. Let the thrust work to keep your docked sections in line.

[Tuareg]

i dont know what you guys dont understand on "oscillating". not wobbly, not unstable... its like this:

and this is a tiny craft, imagine the same with a huge one...

this one is just an empty fueltank. how would it look when full?

[Scoundrel]

This is a well known PID issue with the stock SAS. There's a plugin that deals with it, you'll have to search the forums.

[Tuareg]

mod mod mod. if a modder can deal with it why squad cant?

[prophet_01]

The thing I've noticed is that it's not entirely the SAS's fault. Before 0.90 the SAS behaved differrently. Now it seems to be working as it did in 0.23.5 again (I rly rly like that btw) + orientation functions. It's vastly more agressive now, which is great for instable launches. But on the other hand this seems to be a resson for overshooting and oscilating around the node. I personally prefer how it is now as I don't build ships with 500t in orbit that regulary

Ways to make the SAS work in every situstion, would be to adjust the SAS behaviour automatically once you reach space automatically or to implement button to do that during the mission. For more precise orientation functions (in space), the game would need to be able to adapt the maneuver to a vessels mass and torque

[Jouni]

Stock SAS parameters have been optimized for ships enough control authority. Ships with less control authority often oscillate, it the player uses SAS in a naive way, because SAS starts slowing down too late and overshoots. The easiest fix is to turn manually and to use SAS only intermittently (F instead of T), until the ship has stabilized. (Similar problems may occur if the ship has too much control authority. In those situations, the solution is to build a better ship.)

Docking ports are already rigid enough, considering that they're supposed to be temporary connections made using flat parts. If you want more rigid connections, use multiple docking ports. My biggest ship used seven 2.5 m docking ports to connect the Kerbin escape stage to the rest of the ship.

[prophet_01]

Well, too much authority is not necessarily a design flaw imo. Most leightweight probes or satelites that decouple from a booster stage and only hold a minimum of fuel have that issue. You can't adjust the torque of the SAS right now. I've heard a rumor that this is going to be implemented soon. That will hopefully help the ultra lightweight segment a lot. For rly large ships I prefer manual controls, they are just too whobly and often rather specific regsrding the limitations. Even mechjeb can't be trusted on that scale most of the times

[rkman]

SAS needs a little work. Can't a single configuration of PID parameters is going to be unsuitable for most craft sizes.

'State switching' generally also needs a bit of work, to eliminate phantom forces upon putting a vessel on the pad, coming out of warp, and upon 'jumping the floating origin'. Until then the Kraken may be subdued but it lives.